It is known that for a given gas which is soluble or partially soluble in a given liquid, (i.e., carbon dioxide and water) the rate of solvation of the gas into the liquid increases as the interfacial area between a given volume of the liquid and the gas is increased per given unit of time. For example, far more oxygen dissolves per unit of time into water cascading over a turbulent waterfall than dissolves into the equivalent volume of still water in a pond or lake in the same length of time.
Various methods of carbonating water are know in the prior art. In one such method carbon dioxide gas is injected into the water to be carbonated at a low level forming bubbles which float up through the water to the surface so that carbon dioxide in the bubbles becomes absorbed into the water. This method is often used in small carbonating apparatus for home use where only a limited number of drinks are mixed. Examples of this injection method of carbonation can be seen in UK Patent Specification No. 412,849 (Schwendimann) and U.S. Pat. No. 2,826,401 (Peters). The main problem with this injection method is that it is only effective if relatively high pressures are used in the carbonation chamber during carbonation.
A second known method of carbonating water involves spraying or atomizing the water into an atmosphere of carbon dioxide gas. In this method a carbonation chamber may be prefilled with carbon dioxide and the water introduced into the chamber by spraying or the chamber may be partially filled with water and the water drawn upwardly and sprayed into the carbon dioxide atmosphere above the water level in the chamber. In this method, carbon dioxide is dissolved into the water droplets in the spray and the droplets carry the carbon dioxide in dissolved form into the body of water to effect carbonation. Typical examples of this method are shown in U.S. Pat. No. 2,306,714 (Rowell) and U.S. Pat. No. 2,391,003 (Bowman). A major problem with this method is that it requires the carbonation chamber to be pressurized to a relatively high pressure and a long time is required to achieve sufficient carbonation.
A third known method of carbonation, shown in U.S. Pat. No. 4,719,056 (Scott), involves partly filling a carbonation chamber with water and providing an atmosphere of carbon dioxide above the level of water in the chamber and continuously or repeatedly drawing or forcing gas from said atmosphere down into the water by a rotating member such as a paddle wheel which rotates about a horizontal axis at 1,000 to 1,500 RPM and passes through both the carbon dioxide atmosphere and the water. This mechanical mixing increases the area of interface exposure between the carbon dioxide and water; i e., in comparison to no mixing and causes the water and carbon dioxide to form a solution far more rapidly and to a greater solution concentration than would occur if there were no such mixing of the gas and water. The main disadvantages of this method is that it requires more moving parts, has more chance of malfunction and requires more energy to operate.
It is also known that the carbon dioxide gas solubility rate and dissolved gas concentration level in water increases as the pressure acting upon the liquid gas mix increases.
Finally, within limits, as the temperature of water decreases, the amount of carbon dioxide that can be dissolved into a given volume of water increases. This relationship is shown in Table 10-1 entitled "Solubility of Gases in Water" page 10-4 Langs Handbook of Chemistry 12th Edition. This table shows the solubility of carbon dioxide in milliliters per gram of water to be 0.759 ml at 30.degree. C. (72.degree. F.) and 1.646 ml at 1.degree. C. (34.degree. F.) showing 216 percent more carbon dioxide may be dissolved into the water at 1.degree. C. than at 30.degree. C.
The ideal process, therefore, for rapidly carbonating water with maximum levels of dissolved carbon dioxide would provide for:
a means to cause high interfacial contact between the water and carbon dioxide; PA1 a means to carry out the process at elevated pressure; and PA1 a means to carry out the process with water temperatures where the carbon dioxide gas solution level is highest; i.e., a water temperature range of 1.degree. to 5.degree. C.
The present invention satisfies these conditions at low cost and without the use of mechanical mixers or motors as will be explained later in the specification.